The use of a ball and socket joint as a vehicle level sensor for the contactless and continuous measurement of the changes in the position of the vehicle body in motor vehicle chassis, wherein the ball and socket joint housing and the ball pivot are arranged between the vehicle chassis and the wheel suspension, is known from EP 617 260 A1. It is proposed in that document that the information obtained from the vehicle level sensor be used for headlight leveling control and/or vehicle level control.
The ball and socket joint has a bipolar field transducer arranged at the joint ball of the ball pivot and a magnetoresistive sensor arranged at the ball and socket joint housing in the range affected by the field transducer. The sensor shall detect here the position of the ball pivot or a change in this position, during which the position of the field transducer in relation to the sensor and consequently the magnetic field at the site of the sensor changes, as accurately as possible via the detected field. It is proposed for this purpose that the sensor and the field transducer be arranged opposite each other in the joint ball and in the ball and socket joint housing, so that the measured signals generated reflect the actual changes in the position of the vehicle body, without interference by three-dimensional motions occurring in the axle area of a vehicle.
However, measurement results that are sufficient for the motor vehicle cannot be expected with the one sensor in terms of accuracy in the case of this ball pivot, because the sensor can measure only one direction of motion (degree of freedom) of the ball pivot, and the other two degrees of freedom must be determined by means of electronic evaluation or excluded.
To improve the accuracy of measurement, it is proposed, furthermore, in the patent application DE 101 34 259 A1 that at least two field sensors be arranged in the ball and socket joint housing diametrically opposite each other on an orbit in the area of the ball surface. It is thus possible with the two different poles of the field transducer, which are arranged on the ball surface, to determine a pivoting and rotation about its central axis. To determine the exact position of the ball pivot in space in relation to the ball and socket joint housing in all three degrees of freedom, it is proposed that three field sensors be arranged on the orbit at a distance of 120°.